Transmission type liquid crystal display having an organic interlayer elements film between pixel electrodes and switching

Abstract

The transmission type liquid crystal display device of this invention includes: gate lines; source lines; and switching elements each arranged near a crossing of each gate line and each source line, a gate electrode of each switching element being connected to the gate line, a source electrode of the switching element being connected to the source line, and a drain electrode of the switching element being connected to a pixel electrode for applying a voltage to a liquid crystal layer, wherein an interlayer insulating film formed of an organic film with high transparency is provided above the switching element, the gate line, and the source line, and wherein the pixel electrode formed of a transparent conductive film is provided on the interlayer insulating film.

What is claimed is:  
     
       1. A method for fabricating a transmission type liquid crystal display device, comprising the steps of: 
       forming a plurality of switching elements in a matrix on a substrate;  
       forming a gate line connected to a gate electrode of each switching element and a source line connected to a source electrode of the switching element, the gate line and the source line crossing each other;  
       forming an organic film having a light transmittance of 90% or more for light with a wavelength in the range of about 400 nm to about 800 nm above the switching elements, the gate lines and the source lines by a coating method and patterning the organic film to form an interlayer organic insulating film and contact holes through the interlayer organic insulating film; and  
       forming pixel electrodes formed of transparent conductive films on the interlayer organic insulating film and inside the contact holes so that each pixel electrode overlaps at least partially one or both of the gate line and the source line and is connected to each of the switching elements.  
     
     
       2. A method according to claim  1 , wherein the patterning of the organic film is conducted by 
       exposing the organic film to light and developing the exposed organic film.  
     
     
       3. A method according to claim  2 , wherein the organic film is formed by using a photosensitive transparent acrylic resin which dissolves in a developing solution when exposed to light, and the interlayer organic insulating film and the contact holes are formed by exposing the photosensitive transparent acrylic resin to light and developing the photosensitive transparent acrylic resin. 
     
     
       4. A method according to claim  3 , further including the step of, after the light exposure and development of the organic film, exposing the entire substrate to light for reacting a photosensitive agent contained in the photosensitive transparent acrylic resin, thereby decoloring the photosensitive transparent acrylic resin. 
     
     
       5. A method according to claim  4 , wherein a base polymer of the photosensitive transparent acrylic resin includes a copolymer having methacrylic acid and glycidyl methacrylate and the photosensitive transparent acrylic resin contains a quinonediazide positive-type photosensitive agent. 
     
     
       6. A method according to claim  5 , wherein the interlayer organic insulating film is formed by developing the photosensitive transparent acrylic resin with tetramethyl ammonium hydroxyoxide developing solution with a concentration of about 0.1 mol % to about 1.0 mol %. 
     
     
       7. A method according to claim  3 , further including the step of, after the formation of the contact holes through the interlayer organic insulating film, decoloring the interlayer organic insulating film by irradiating the interlayer organic insulating film with ultraviolet light. 
     
     
       8. A method according to claim  3 , further including the step of, before the formation of the organic film, forming a silicon nitride film on a surface of the substrate where the organic film is to be formed. 
     
     
       9. A method according to claim  2 , wherein the organic film has a thickness of about 1.5 μm or more. 
     
     
       10. A method according to claim  2 , further including the step of, before the formation of the organic film, irradiating with ultraviolet light a surface of the substrate where the organic film is to be formed. 
     
     
       11. A method according to claim  2 , further including the step of, before the formation of the organic film, applying a silane coupling agent on a surface of the substrate where the organic film is to be formed. 
     
     
       12. A method according to claim  2 , wherein the material for forming the organic film contains a silane coupling agent. 
     
     
       13. A method according to claim  12 , wherein the silane coupling agent includes at least one hexamethyl disilazane, dimethyl diethoxy silane, and n-buthyl trimethoxy silane. 
     
     
       14. A method according to claim  2 , further including the step of, before the formation of the pixel electrode, ashing the surface of the interlayer organic insulating film by an oxygen plasma. 
     
     
       15. A method according to claim  14 , wherein the ashing step is conducted after the formation of the contact holes. 
     
     
       16. A method according to claim  14 , wherein the interlayer organic insulating film includes a thermally curable material and the interlayer organic insulating film is cured before the ashing step. 
     
     
       17. A method according to claim  14 , wherein the thickness of the ashed portion of the interlayer organic insulating film is in the range of about 100 to 500 nm. 
     
     
       18. A method according to claim  2 , wherein the thickness of the pixel electrode is about 50 nm or more. 
     
     
       19. A method according to claim  1 , wherein the patterning of the organic film is conducted by etching the organic film by using a photoresist on the organic film as an etching mask. 
     
     
       20. A method according to claim  19 , wherein the organic film has a thickness of about 1.5 μm or more. 
     
     
       21. A method according to claim  19 , wherein the thickness of the pixel electrode is about 50 nm or more. 
     
     
       22. A method according to claim  19 , wherein the patterning of the organic film includes the steps of: 
       forming a photoresist layer containing silicon on the organic film;  
       patterning the photoresist layer; and  
       etching the organic film by using the patterned photoresist layer as an etching mask.  
     
     
       23. A method according to claim  22 , wherein the etching step is a step of dry etching using an etching gas containing at least one of CF 4 , CF 3 H and SF 6 . 
     
     
       24. A method according to claim  19 , wherein the patterning of the organic film includes the steps of: 
       forming a photoresist layer on the organic film;  
       coating a silane coupling agent on the photoresist layer and oxidizing the coupling agent;  
       patterning the photoresist layer; and  
       etching the organic film by using the patterned photoresist layer covered with the oxidized coupling agent as an etching mask.  
     
     
       25. A method according to claim  24 , wherein the etching step is a step of dry etching using an etching gas containing at least one of CF 4 , CF 3 H and SF 6 .